DNA supercoiling, a critical signal regulating the basal expression of the lac operon in Escherichia coli

Authors

Geraldine Fulcrand, Biomolecular Sciences Institute and Department of Chemistry and Biochemistry, Florida International University
Samantha Dages, Biomolecular Sciences Institute and Department of Chemistry and Biochemistry, Florida International UniversityFollow
Xiaoduo Zhi, Biomolecular Sciences Institute and Department of Chemistry and Biochemistry, Florida International UniversityFollow
Prem Cheapagain, Biomolecular Sciences Institute and Department of Physics, Florida International UniversityFollow
Bernard S. Gerstman, Biomolecular Sciences Institute and Department of Physics, Florida International UniversityFollow
David Dunlap, Emory University
Fenfei Leng, Biomolecular Sciences Institute and Department of Chemistry and Biochemistry, Florida International UniversityFollow

Date of this Version

1-14-2016

Document Type

Article

Rights

by

Abstract

Escherichia coli lac repressor (LacI) is a paradigmatic transcriptional factor that controls the expression of lacZYA in the lac operon. This tetrameric protein specifically binds to the O1, O2 and O3 operators of the lac operon and forms a DNA loop to repress transcription from the adjacent lac promoter. In this article, we demonstrate that upon binding to the O1 and O2 operators at their native positions LacI constrains three (−) supercoils within the 401-bp DNA loop of the lac promoter and forms a topological barrier. The stability of LacI-mediated DNA topological barriers is directly proportional to its DNA binding affinity. However, we find that DNA supercoiling modulates the basal expression from the lac operon in E. coli. Our results are consistent with the hypothesis that LacI functions as a topological barrier to constrain free, unconstrained (−) supercoils within the 401-bp DNA loop of the lac promoter. These constrained (−) supercoils enhance LacI’s DNA-binding affinity and thereby the repression of the promoter. Thus, LacI binding is superhelically modulated to control the expression of lacZYA in the lac operon under varying growth conditions.

DOI

10.1038/srep19243

Identifier

FIDC001622

Comments

Originally published in Scientific Reports.

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 License.

Recommended Citation

Fulcrand, Geraldine; Dages, Samantha; Zhi, Xiaoduo; Cheapagain, Prem; Gerstman, Bernard S.; Dunlap, David; and Leng, Fenfei, "DNA supercoiling, a critical signal regulating the basal expression of the lac operon in Escherichia coli" (2016). Biomolecular Sciences Institute: Faculty Publications. 15.
https://digitalcommons.fiu.edu/biomolecular_fac/15